Effect

Generation I

Bonemerang inflicts damage, hitting the target twice per use. Although only the first strike can be a critical hit, the second one will deal the same amount of damage.

Bonemerang will end immediately if the first strike breaks a substitute. Bide and Counter will only acknowledge the second strike of this move.

Generation II

Each strike now does damage independently, consequently enabling either of them to be critical.

Generations III and IV

Bonemerang will now hit again if the first strike breaks a substitute.

Generation V

If the first strike activates the target's Focus Sash, Focus Band, or Sturdy, the second one will cause the defending Pokémon to faint. A Focus Band can still activate again to prevent fainting, but this chance is independent of the previous one.